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Can this food additive turn our gut bacteria against us?

Titanium dioxide nanoparticles make up a common additive — E171 — used as a coloring agent in many products. So far, the additive's safety has been a matter of debate, but new research in mice has found evidence that it could render the gut more susceptible to disease.

A common food additive in white cake icing could 'prime' the gut for disease.

E171 is a food additive that manufacturers use to whiten various products, including chewing gum, cake icing, and candy, for instance.

While the addition of this substance may render certain products more appealing, there is an ongoing debate about its safety.

France, for instance, will ban the use of E171 in food products starting next year, over concerns that the additive could lead to health problems.

Moreover, a study in vitro, published in the journal Environmental Science: Nano in April this year, also found that E171 can lead to the alteration of normal cell function and upkeep in the gastrointestinal tract, which could mean that the substance can damage the gut's self-protective mechanisms.

This month, another study conducted in mice has uncovered new evidence that this common additive can "prime" the gut for disease.

The research — the results of which appear in Frontiers in Nutrition — explains how E171 can alter the activity of gut bacteria in potentially dangerous ways.

"It is well established that dietary composition has an impact on physiology and health, yet the role of food additives is poorly understood," notes co-lead author Wojciech Chrzanowski, Ph.D., who is an associate professor at the University of Sydney in Australia.

"There is increasing evidence that continuous exposure to nanoparticles has an impact on gut microbiota composition, and since gut microbiota is a gatekeeper of our health, any changes to its function have an influence on overall health," he continues.

The additive alters the behavior of bacteria

"The aim of this research is to stimulate discussions on new standards and regulations to ensure safe use of nanoparticles in Australia and globally," explains Chrzanowski.

Chrzanowski and colleagues administered E171 to the mice in their water, then assessed the substance's effect on the gut microbiota. The investigators also conducted some experiments in vitro.

They found that the titanium dioxide particles had little to no impact on the composition of the gut microbiota.

However, in assessing the mice, they noticed that the substance affected the release of microbial metabolites — molecules produced by the bacteria — which interact with their biological environment, acting as messengers between the gut bacteria and their host.

In vitro experiments also showed that titanium dioxide altered the distribution of bacteria in the gut, which led to the formation of biofilm. This is a sticky "network" that alters the way in which the bacteria act, and it can also influence the immune system's response to infection.

Moreover, biofilms do not respond to usual methods of treatment, such as antibiotics, which can render them a fierce foe to be reckoned with.

"This study investigated effects of titanium dioxide on gut health in mice and found that titanium dioxide did not change the composition of gut microbiota, but instead it affected bacteria activity and promoted their growth in a form of undesired biofilm," explains the study's other co-lead author, associate professor Laurence Macia, Ph.D.

"Biofilms are bacteria that stick together, and the formation of biofilm has been reported in diseases such as colorectal cancer," Macia notes.

'Pivotal evidence' that E171 is harmful

The changes that the researchers saw titanium dioxide making in the gut environment were also associated with markers of inflammation in the colon, meaning that the substance was able to "prime" the gut for disease.

"This study presents pivotal evidence that consumption of food containing food additive E171 (titanium dioxide) affects gut microbiota as well as inflammation in the gut, which could lead to diseases such as inflammatory bowel diseases and colorectal cancer."

Wojciech Chrzanowski, Ph.D.

According to Macia, the current research shows "that titanium dioxide interacts with bacteria in the gut and impairs some of their functions, which may result in the development of diseases."

Looking at the results of the study, its authors explain that E171 is not harmless and that its potential effects on health should be recognized and addressed by officials.

"We are saying that its consumption should be better regulated by food authorities," Macia emphasizes.

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